The poison gland is analogous to the parotid in location and structure. The duct which runs through it is so dilated as to contain a small amount of the peculiar poison. The amount of poison contained in these reservoirs varies from eight to twelve minims, and is secreted somewhat slowly. It seems to be, in some cases at least, a _glucoside_; in others, a _toxalbumin_. It is capable of being preserved either dry or in alcohol or in glycerin. The active poisonous principle seems to pertain to a _globulin_ or to a _peptone_. Almost all of these venoms are innocuous if swallowed, and like septic infections seem inoculable only through the tissues and the circulating fluids. According to Mitchell, the venom of the rattlesnake renders the blood incoagulable, paralyzes the walls of the capillaries, and facilitates escape of leukocytes into the tissues, thus making actual hemorrhagic swelling occur; while the red corpuscles rapidly lose shape and fuse into irregular masses and their hemoglobin is dissolved or disappears. This poison seems to paralyze both the respiratory centre and the heart. Cobra poison, not containing globulin, at least to a great extent, does not produce the rapid changes of rattlesnake poison. =Symptoms.=--A snake bite is like a hypodermic injection of a deadly poison, and symptoms set in promptly. These are both local and general. There is more or less local pain, with swelling and discoloration, which are due to effusion of blood. They increase in intensity, and are followed by vesication and necrosis of tissues--that is, gangrene--if the patient survive for some time. Constitutional symptoms are not long delayed, and are characterized by severe prostration, including cold, clammy sweat; feeble and rapid pulse, irregular respiration, etc. When patients succumb they usually die in collapse. The pathological changes are not well-marked or characteristic.